Accurate computation of a centroid from a pre-defined window in an image plane is desirable for a number of space-based and commercial applications. The applications may include object tracking in robotic systems, autonomous navigation, image compression, and document copyright protection. Other applications may include space guidance and navigation systems, and deep-space optical communication systems that require accurate and stable beam pointing for high speed data transfer.
Off-focal-plane digital processors may yield accurate centroid values, but only at the cost of increased latency, power and size. On or near focal-plane centroid computation using current mode circuits, and neuro-MOS circuits have been implemented. However, neither approach may be compatibly integrated with high performance image sensors.
A photodiode-based active pixel imager (API) sensor may be used for high quality imaging applications such as the centroid computation. The photodiode-based sensor provides higher quantum efficiency than a photogate-based sensor. However, noise in the photodiode-type CMOS API sensors causes high reset (kTC) noise at the sense node.
The present disclosure describes a centroid computation system having an imager array, a switching network, computation elements, and a divider circuit. The imager array has columns and rows of pixels. The switching network is adapted to receive pixel signals from the image array. The plurality of computation elements operates to compute inner products for at least x and y centroids. The plurality of computation elements has only passive elements to provide inner products of pixel signals the switching network. The divider circuit is adapted to receive the inner products and compute the x and y centroids.